Susceptor with ring to limit backside deposition

ABSTRACT

A susceptor including a generally circular body having a face with a radially inward section and a radially outward section proximate a circumference of the body, the radially outward section having at least one ring extending upward for contacting a bottom surface of a substrate, and wherein the radially inward section lacks a ring extending upward from the face.

FIELD OF THE INVENTION

This disclosure relates generally to semiconductor processing, and moreparticularly to susceptors for supporting semiconductor substrates inprocess chambers.

BACKGROUND

Semiconductor fabrication processes are typically conducted with thesubstrates supported within a chamber under controlled conditions. Formany purposes, semiconductor substrates (e.g., wafers) are heated insidethe process chamber. For example, substrates can be heated by directphysical contact with an internally heated wafer holder or “chuck.”“Susceptors” are wafer supports used in radiantly heated systems wherethe wafer and susceptors absorb radiant heat.

Susceptors are commonly formed by machining graphite into a desiredshape and applying a silicon carbide (SiC) Coating. Susceptors can beformed in different shapes, but many are circular.

A number of quality control issues can arise during processing,including but not limited to substrate sliding, sticking, curling, andbackside deposition. Slide occurs during drop off when a cushion of gasin the susceptors recess or pocket is unable to escape fast enough toallow the substrate to fall immediately onto the susceptor. Thesubstrate floats momentarily above the susceptor as the gas slowlyescapes, and it tends to slide off center. Thus, the substrate may notrest in the center of the pocket where it was intended, and unevenheating of the substrate may result.

Backside deposition occurs when process gases work into the spacebetween the substrate and the susceptor and are able to deposit on aback surface of the substrate. Because the flow of the process gases isnot controlled between the substrate and the susceptor, randomdeposition can occur on the backside of the substrate. This randomdeposition can create thickness inconsistencies on the backside, whichcan affect local site flatness on the frontside, and ultimately devicethickness issues.

SUMMARY

Various aspects and implementations are disclosed herein that relate tosusceptor designs and methods for processing with susceptors. In oneaspect, a susceptor including a generally circular body having a facewith a radially inward section and a radially outward section proximatea circumference of the body, the radially outward section having atleast one ring extending upward from the face for contacting a bottomsurface of a substrate, and wherein the radially inward section lacks aring extending upward from the face.

In an implementation, the at least one ring may be a plurality of ringsconcentrically disposed on the radially outward section. The at leastone ring may be at least six rings. The radially outward section may beangled with respect to the radially inward section. The angle may beapproximately three degrees. The at least six rings may be spaced apartfrom one another by approximately 0.5 mm.

The radially inward portion may further include a gridded surfaceextending upward from the face. The gridded surface may be at leastpartially concave in shape. The gridded surface may further include aplurality of protrusions spaced apart approximately 1.25 mm from oneanother. Each of the plurality of protrusions may further include angledouter walls. The radially inward section surface area may beapproximately 1600 times larger than the radially outward sectionsurface area. The radially outward section may further include ashoulder extending upward above the at least one ring at a positionoutside the at least one ring. The at least one ring may be a continuousring. The at least one ring may further include a constant radius.

In another aspect, a reaction system includes a substrate holderincluding a body having a top surface and a bottom surface, the topsurface having a radially inward section with a gridded surfaceextending upward from the radially inward section, the top surfacehaving a radially outward section with at least one ring extendingupward from the radially outward section, and wherein the radiallyoutward section is angled with respect to the radially inward section.

The at least one ring may be at least six rings, each ring arrangedseparate from one another and being continuously disposed on theradially outward section. The gridded surface may be composed of aplurality of protrusions and wherein a top of each of the plurality ofprotrusions defines a substrate contact surface.

In still another aspect, a method of supporting a substrate includes thesteps of providing a susceptor in a reaction chamber, the susceptorincluding a radially inward section having a face for receiving thesubstrate, the face having a gridded surface extending upward and aradially outward section having at least one ring extending upward,positioning the substrate above the susceptor, locating the substrate incontact with the gridded surface and the at least one ring, limiting abackside deposition with the contact between the at least one ring andthe substrate, and limiting lateral movement of the substrate to 2 mmwith the contact between the gridded surface and the substrate.

The susceptor radially outward section may be angled with respect to theradially inward section. The susceptor at least one ring may be at leastfive rings.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. Furthermore,the claimed subject matter is not limited to implementations that solveany or all disadvantages noted in any part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a cross-section of a semiconductor processmodule according to an embodiment of the present disclosure.

FIG. 2 is a perspective view of a susceptor top side according to anembodiment of the present disclosure.

FIG. 3 is a perspective view of a susceptor bottom side according to anembodiment of the present disclosure.

FIG. 4 is an enlarged view of the section labeled FIG-4 in FIG. 2.

FIG. 5 is an enlarged view of a substrate positioned on the susceptortaken generally about line 5-5 in FIG. 4.

FIG. 6 is an enlarged view of the section labeled FIG-6 in FIG. 4 with asubstrate in dashed lines.

FIG. 7 schematically shows a cross-section of a semiconductor processmodule according to an embodiment of the present disclosure.

FIG. 8 is a perspective view of a susceptor top side according to anembodiment of the present disclosure.

FIG. 9 schematically shows a cross-section of a semiconductor susceptoraccording to an embodiment of the present disclosure during one phase ofthe processing.

DETAILED DESCRIPTION

The present aspects and implementations may be described in terms offunctional block components and various processing steps. Suchfunctional blocks may be realized by any number of hardware or softwarecomponents configured to perform the specified functions and achieve thevarious results. For example, the present aspects may employ varioussensors, detectors, flow control devices, heaters, and the like, whichmay carry out a variety of functions. In addition, the present aspectsand implementations may be practiced in conjunction with any number ofprocessing methods, and the apparatus and systems described may employany number of processing methods, and the apparatus and systemsdescribed are merely examples of applications of the invention.

FIGS. 1-7 illustrate a first aspect susceptor 10 positioned within asemiconductor processing environment 12 having a reaction chamber (orprocessing chamber) 14 with an upper chamber 16 and a lower chamber 18.Referring to FIG. 1, reaction chamber 14 includes walls 20 forming atleast a portion of the outer perimeter of each chamber and may becomposed of any suitable material, including but not limited to quartz.A heating element housing 22 may be formed in upper chamber 16 abovesusceptor 10 to secure radiant heating elements 24 to produce heat 26directed at susceptor 10 and a workpiece 28 (e.g., a substrate orsemiconductor wafer).

Susceptor 10 may be secured directly to an elevator 30 through susceptormount 32 to permit vertical positioning of the susceptor 10 andworkpiece 28 thereon. Further, while not shown, a heating element may belocated adjacent susceptor 10 without departing from the spirit andscope of the disclosure.

Upper chamber 16 may be fed a reactant or precursor material 34, such asTrichlorosilane (TCS) with a carrier gas such as H₂ or any othersuitable precursor or carrier gases, through gas line 36 by pump 38.Precursor 34 is feed through upper chamber 16 in the directionassociated with arrows 40 until reaching exhaust aperture 42 andultimately exhaust port 44, thereby providing a laminar flow of processgases through the reaction chamber 14, which can function as a laminarflow reaction chamber. In a similar fashion, a second precursor source46 may be hydrogen chloride (HCl) with an H₂ carrier or any othersuitable precursor which is pumped through gas line 48 by pump 50.Precursor 46 is then introduced into lower chamber 18 in the directionassociated with arrows 52 where it then may escape to the upper chamberthrough gaps between the susceptor and a graphite ring and between thegraphite ring and the quartz chamber, not specifically shown. Precursor46 may then exit through exhaust aperture 42 and exhaust outlet 44.

While not specifically shown, the reaction chamber may be a singlechamber instead of a split chamber, or may be a reduced volume chamber,or any combination of chamber attributes. Further, precursor 46 may bearranged to include a separate exhaust port if intermingling of theprecursors is not desired. In addition, one or more other precursors orprocess gases may be connected in gas communication with the gas lines36 or 48, as desired, to provide the additional gas species forprocesses performed in the chamber 16.

FIGS. 2 and 3 illustrate top and bottom views respectively of susceptor10 having a face or top surface 54, a bottom surface 56, and a sidesurface 58. Top surface 54 may include a radially inward section 60 anda radially outward section 62 extending from the face of the susceptor10. Radially inward section 60 may include a plurality of protrusions 64spaced apart from one another. Radially outward section 62 is proximatea circumference of the susceptor 10 and may include at least one ring 66extending upwards from the face at an angled portion 68. In one aspect,the angled portion 68 extends from the outer perimeter of the radiallyinward section 60 until the termination of the at least one ring 66. Ina preferred implementation, anywhere from one to ten rings 66 extendupward from the radially outward section 62. A shoulder 70 may belocated adjacent the at least one ring 66 to form the remainder of theradially outward section 62.

Referring to FIG. 3, bottom surface 56 of susceptor 10 may includeapertures 72 to connect the susceptor 10 to the elevator 30 (FIG. 1) anda plurality of holes 74 or other suitable passageway to permit processgas to pass through the susceptor body. While only a few holes 74 arelabeled, any suitable number and orientation of holes 74 may beutilized. Further, any suitable number of apertures 72 may be utilized,including zero if the susceptor 10 is mounted to a heater and notdirectly mounted to an elevator. The bottom surface 56 is also shownhaving generally inward and outward sections due to the placement ofholes 74. In the event no holes are utilized, or as desired for theprocessing application, there need not be a noticeable division betweenthe radially inward and radially outward sections 60 and 62.

Referring now to FIG. 4, an enlarged view of the interchange betweenradially inward section 60 and radially outward section 62 is shown ingreater detail. Protrusions 64 are shown extending in a grid-likefashion along the face of radially inward section 60 with grooves 65formed between each set of protrusions 64. Near the interchange of theradially inward and outward sections 60 and 62, protrusions 64 may beelongated as shown near rings 66 to provide a consistent surface for aworkpiece (not shown in this FIG). Each protrusion 64 is preferablyevenly spaced apart from adjacent protrusions to provide bothconsistency through the wafer and from wafer to wafer.

In one aspect, a gridded susceptor face with protrusions 64 may functionto create grooves 65 that function as a cavity for providing acushioning gas during wafer loading. The protrusions may be configuredto provide a volume of gas underneath the wafer to allow gas to compressand escape, to minimize wafer sliding when a wafer is placed on asusceptor, and for gas to expand and flow in under the wafer to minimizewafer sticking when the wafer is lifted from the susceptors. U.S. Pat.No. 7,601,224, assigned to ASM America, Inc. issued on Oct. 13, 2009describes the cushioning gas procedure in more detail and the disclosureof which is hereby incorporated herein by reference.

FIG. 5 illustrates workpiece 28 resting on susceptor 10 for processing.Specifically, a bottom surface 76 of workpiece 28 is resting on rings 66and may be contacting protrusions 64. Workpiece 28 also includes a topsurface 78 and a side surface 80, wherein side surface 80 may beadjacent shoulder 70 of susceptor 10 and top surface 78 may bepositioned above shoulder 70 during processing. Advantageously, thisarrangement permits process gases to minimally contact side surface 80and appropriately contact top surface 78 for wafer processing. Asfurther shown, precursor 46 may travel in the direction associated witharrows 82 through holes 74 in susceptor 10 and contact bottom surface76.

Referring to FIG. 6, protrusions 64 are illustrated having angledsidewalls 84 terminating at top wall 86. The array of protrusions 64 arearranged to provide a generally gridded surface which extends upwardfrom the face of the susceptor 10 and provides a contact surface for theworkpiece backside 76 after a cushioning gas is dissipated. Theprotrusions 64 are spaced apart from one another a suitable distance,which may be approximately 0.1 to approximately 10 millimeters, and ispreferably approximately 1.25 millimeters. Still further, protrusions 64may be arranged to be at least partially concave in shape to assist inworkpiece locating. The concave shape may occur due to a curved surfacewhere protrusions 64 extend upwards from, or by varying the height andshape of protrusions 64 as they extend upwards from outside to thecenter of the susceptor.

Radially outward of protrusions 64 are rings 66 which are concentricallydisposed on radially outward section 62. In one aspect, the rings arespaced apart a distance Y from one another anywhere from approximately0.05 to approximately 5 millimeters and preferably approximately 0.5 mmRings 66 may be continuously disposed on the radially outward section 62and may include a constant radius for consistent workpiece locating.Radially outward section 62 may also be oriented at an angle X fromapproximately zero to approximately ten degrees, and preferablyapproximately three degrees. Due to the relatively small size ofradially outward section 62, radially inward section 60 may have asurface area approximately 1600 times larger than the radially outwardsection.

In operation, rings 66 are useful to help reduce backside deposition onthe workpiece and particularly the backside 76 of the workpiece 28.Rings 66 ensure a continuous ridge contacts the backside of theworkpiece near the circumference of the workpiece to prevent process gasfrom reaching the backside 76 of the workpiece 28. Protrusions 64, onthe other hand, provide grip on the workpiece during processing,workpiece loading, and workpiece unloading. While FIG. 6 does notexplicitly illustrate protrusions 64 contacting workpiece 28, suchcontact is envisioned within the spirit and scope of the disclosure. Theseparation illustrated is merely to provide a better understanding ofthe disclosure. Specifically, during workpiece loading and unloading,protrusions 64 greatly reduce workpiece slippage by allowing gas flowbetween the protrusions and providing a constant contact surface afterthe cushioning gas dissipates to limit lateral movement to less than 2mm in any direction. Advantageously, the workpiece 28 is processed moreconsistently because the workpiece 28 does not slip during loading andbackside deposition is greatly reduced.

A method of supporting workpiece 28 may include providing susceptor 10with radially inward section 60 and radially outward section 62 inreaction chamber 14 (FIG. 1) with at least one ring 66 extending upwardin the radially outward section 62 and arranged to receive workpiece 28.The workpiece 28 is initially positioned above susceptor 10 andworkpiece 28 is then located in contact with protrusions 64 (the griddedsurface) and rings 66. The contact of workpiece 28 and rings 66 ofsusceptor 10 limits backside deposition on the workpiece 28 and thecontact between workpiece 28 and protrusions 64 limits lateral movementof the workpiece 28. Still further, the radially outward section 62 ofsusceptor 10 may be angled with respect to the radially inward section60 to further limit backside deposition on the workpiece 28. Stillfurther, the specific number of rings 66 may be at least five rings.

Referring to FIGS. 7-9, susceptor 100 is shown with shoulder 70 adjacentrings 66 and a plurality of angled holes 88 extending through theradially inward section 60. Angled holes 88 extend from lower chamber 18into backside processing area 92. During processing, a first process gaspasses across wafer top surface 78 in the direction associated witharrows 90, while a second process gas passes through lower chamber 18through angled holes 88 and into backside processing area 92 where thesecond process gas contacts a wafer bottom 76. This second process gastravels in the direction associated with arrows 94 and may leave thebackside processing area 92 adjacent the susceptor 100 and wafer 28 orback through the lower chamber 18 as discussed above.

While the angled holes 88 are illustrated as angled, any suitableorientation may be utilized, including straight holes or any anglebetween. In one aspect, the lower chamber process gas may be hydrogenchloride (HCl) and is used to etch the bottom or backside 76 of wafer 28to maintain a constant and consistent wafer backside. Further,maintaining a consistent wafer backside is important because itdetermines the overall thickness of the wafer and can create thicknessirregularities. Thus, during a deposition step, HCl can be added to thelower chamber to reduce backside deposition, while between or after adeposition step, HCl can be used to etch the backside of any depositionthereon. While HCl has been highlighted as one potential etchant, anysuitable etching chemistry may be utilized without departing from thespirit and scope of the disclosure.

These and other embodiments for methods and apparatus for a susceptor toreduce wafer sliding and backside deposition may incorporate concepts,embodiments, and configurations as described with respect to embodimentsof apparatus for susceptors described above. The particularimplementations shown and described are illustrative of the inventionand its best mode and are not intended to otherwise limit the scope ofthe aspects and implementations in any way. Indeed, for the sake ofbrevity, conventional manufacturing, connection, preparation, and otherfunctional aspects of the system may not be described in detail.Furthermore, the connecting lines shown in the various figures areintended to represent exemplary functional relationships and/or physicalcouplings between the various elements. Many alternative or additionalfunctional relationship or physical connections may be present in thepractical system, and/or may be absent in some embodiments.

As used herein, the terms “comprises”, “comprising”, or any variationthereof, are intended to reference a non-exclusive inclusion, such thata process, method, article, composition or apparatus that comprises alist of elements does not include only those elements recited, but mayalso include other elements not expressly listed or inherent to suchprocess, method, article, composition or apparatus. Other combinationsand/or modifications of the above-described structures, arrangements,applications, proportions, elements, materials or components used in thepractice of the present invention, in addition to those not specificallyrecited, may be varied or otherwise particularly adapted to specificenvironments, manufacturing specifications, design parameters or otheroperating requirements without departing from the general principles ofthe same.

1. A method of supporting a substrate comprising the steps of: providinga susceptor in a reaction chamber, the susceptor comprising a radiallyinward section having a face for receiving the substrate, the facehaving a gridded surface extending upward and a radially outward sectionhaving at least one ring extending upward; positioning the substrateabove the susceptor; locating the substrate in contact with the face;limiting a backside deposition with the contact between the at least onering and the substrate; and, limiting lateral movement of the substrateto less than 2 mm with the contact between the gridded surface and thesubstrate.
 2. The method of claim 1, wherein the radially outwardsection is angled with respect to the radially inward section.
 3. Themethod of claim 1, wherein the at least one ring is at least five rings.4. The method of claim 1, wherein limiting the backside depositioncomprises controlling a flow of gas between the substrate and thesusceptor.
 5. The method of claim 1, wherein the radially outwardsection is angled with respect to the radially inward section.
 6. Themethod of claim 5, wherein the angle is approximately three degrees. 7.The method of claim 1, wherein the radially inward portion furthercomprises a gridded surface extending upward from the face.
 8. Themethod of claim 7, wherein the gridded surface is at least partiallyconcave in shape.
 9. The method of claim 1, wherein the gridded surfacefurther comprises a plurality of protrusions spaced apart from oneanother.
 10. The method of claim 9, wherein each of the plurality ofprotrusions further comprises angled outer walls.
 11. The method ofclaim 1, wherein at least one ring has a constant radius.
 12. A methodof supporting a substrate comprising the steps of: providing a susceptorin a reaction chamber, the susceptor comprising: a generally circularbody having a face with a radially inward section and a radially outwardsection proximate a circumference of the body, the radially outwardsection having a plurality of plateaus, wherein the plateaus definecontinuous rings as seen in a top down view, wherein each continuousring extends upward for contacting a bottom surface of a substrate,wherein each continuous ring comprises a continuous loop of solidmaterial extending up uniformly to an associated height, wherein theassociated height of each successive continuous ring is successivelylower with decreasing distance to the radially inward section, whereinthe radially inward section comprises a perimeter defined by an angledsidewall concentric with a most inward of the continuous rings, whereinthe angled sidewall comprises a plurality of holes extending through thebody and wherein the angled sidewall comprises a plurality of inwardlyprotruding elongated protrusions, and wherein, upon retention of thesubstrate on an associated one of the continuous rings, the associatedone of the continuous rings contacts the bottom surface of the substrateto prevent gases from reaching the bottom surface; positioning thesubstrate above the susceptor; and locating the substrate in contactwith the face of the generally circular body.
 13. The method of claim12, limiting a backside deposition with the contact between the at leastone ring and the substrate.
 14. The method of claim 13, wherein limitingthe backside deposition comprises controlling a flow of gas between thesubstrate and the susceptor.
 15. The method of claim 12, furthercomprising limiting lateral movement of the substrate to less than 2 mmwith the contact between the gridded surface and the substrate.
 16. Themethod of claim 12, wherein the radially outward section is angled withrespect to the radially inward section.
 17. The method of claim 12,wherein the radially outward section is angled with respect to theradially inward section.
 18. The method of claim 12, wherein theradially inward portion further comprises a gridded surface extendingupward from the face.
 19. The method of claim 18, wherein the griddedsurface is at least partially concave in shape.
 20. The method of claim12, wherein the gridded surface further comprises a plurality ofprotrusions spaced apart from one another.